The present invention relates generally to combine harvesters and, more particularly, to improvements in the cleaning apparatus to permit a fore-and-aft leveling thereof when the combine is operating under fore-and-aft inclined operating conditions.
The operation of combine harvesters under non-horizontal conditions is somewhat less efficient than the operation of the combine on generally level ground because of the gravity induced movement of threshed grain in a downhill direction on the cleaning apparatus. This gravity induced movement creates an unbalanced loading of the cleaning mechanism and prevents a proper flow of air from a cleaning fan through the threshed grain on the sieves to facilitate a removal of chaff and other debris. A fore-and-aft inclination of the sieves will result in the threshed grain being either retarded on the sieves or rushed toward the rearward end, which results in improper cleaning action and/or high grain losses.
Attempts to maintain a combine cleaning apparatus in a horizontal orientation while the combine is operating under sidehill conditions can be found in U.S. Pat. No. 3,731,470 granted to G. K. Cornish et al on May 8, 1973, and in U.S. Pat. No. 4,344,443 granted to C. R. J. DeBusscher on Aug. 17, 1982. The apparatus disclosed in the Cornish patent provides a leveling of the entire frame of the combine through the operation of hydraulic cylinders to maintain the cleaning apparatus in a generally horizontal orientation. Since the entire combine is maintained in a level orientation, it was necessary to modify the connection of the crop harvesting header to the combine to permit a proper gathering of the crop material to be harvested. The apparatus disclosed in the DeBusscher patent provides for a leveling of the entire cleaning mechanism, including the fan, about a longitudinally extending pivot axis; however, the DeBusscher mechanism does not provide for fore-and-aft leveling of the cleaning apparatus. Furthermore, the DeBusscher mechanism is expensive to manufacture, is cumbersome to operate and results in an unnecessary shifting of major structural components.